Cell Swelling Stimulates Cytosol to Membrane Transposition of ICln

Ritter, Markus; Ravasio, Andrea; Jakab, Martin; Chwatal, Sabine; Fürst, Johannes; Laich, Andreas; Gschwentner, Martin; Signorelli, Sara; Burtscher, Carmen; Eichmüller, Sonja; Paulmichl, Markus

doi:10.1074/jbc.m300374200

Cited by 54 publications

(91 citation statements)

References 55 publications

(73 reference statements)

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“…Perhaps in the absence of erythroid protein 4.1 protein, this interaction is altered, resulting in constitutive activation of the exchanger, as shown for CHP2, an isoform of CHP (22). Previous reports on interactions of protein 4.1 with other noncytoskeletal membrane proteins have shown an interaction between the 30-kDa FERM (Four4.1/Ezrin/Radixin/Moesin) domain of erythroid protein 4.1, which mediates cytoskeletalmembrane interactions, and pICln (protein that induces an outwardly rectifying, nucleotide-sensitive chloride current), a cytosolic protein believed to regulate volume-sensitive anion channels (28,31). The crystal structure of this region of protein 4.1 has been solved recently, and the specific sites of interaction with band 3, glycophorin C/D, and the PDZ (PSD95/Dlg/ ZO-1) domain containing the protein p55 binding site have been mapped.…”

Section: Discussionmentioning

confidence: 99%

Effect of complete protein 4.1R deficiency on ion transport properties of murine erythrocytes

Rivera¹,

Franceschi²,

Peters³

et al. 2006

American Journal of Physiology-Cell Physiology

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Moderate hemolytic anemia, abnormal erythrocyte morphology (spherocytosis), and decreased membrane stability are observed in mice with complete deficiency of all erythroid protein 4.1 protein isoforms (4.1−/−; Shi TS et al. J Clin Invest 103: 331, 1999). We have examined the effects of erythroid protein 4.1 (4.1R) deficiency on erythrocyte cation transport and volume regulation. 4.1−/−mice exhibited erythrocyte dehydration that was associated with reduced cellular K and increased Na content. Increased Na permeability was observed in these mice, mostly mediated by Na/H exchange with normal Na-K pump and Na-K-2Cl cotransport activities. The Na/H exchange of 4.1−/−erythrocytes was markedly activated by exposure to hypertonic conditions (18.2 ± 3.2 in 4.1−/−vs. 9.8 ± 1.3 mmol/1013cell × h in control mice), with an abnormal dependence on osmolality (EC50= 417 ± 42 in 4.1−/−vs. 460 ± 35 mosmol/kgH2O in control mice), suggestive of an upregulated functional state. While the affinity for internal protons was not altered (K0.5= 489.7 ± 0.7 vs. 537.0 ± 0.56 nM in control mice), the Vmaxof the H-induced Na/H exchange activity was markedly elevated in 4.1−/−erythrocytes ( Vmax91.47 ± 7.2 compared with 46.52 ± 5.4 mmol/1013cell × h in control mice). Na/H exchange activation by okadaic acid was absent in 4.1−/−erythrocytes. Altogether, these results suggest that erythroid protein 4.1 plays a major role in volume regulation and physiologically downregulates Na/H exchange in mouse erythrocytes. Upregulation of the Na/H exchange is an important contributor to the elevated cell Na content of 4.1−/−erythrocytes.

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Section: Discussionmentioning

confidence: 99%

Effect of complete protein 4.1R deficiency on ion transport properties of murine erythrocytes

Rivera¹,

Franceschi²,

Peters³

et al. 2006

American Journal of Physiology-Cell Physiology

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“…Furthermore, ICln-specific antibodies (5) or antisense oligodeoxynucleotides (17,18) leading to a specific knock-down of the ICln protein impair regulatory volume decrease (RVD) 1 in native cells. Conversely, overexpression of ICln in mammalian cells increases RVD currents during a hypotonic challenge (2,19,20). In bacteria, overexpression of ICln leads to an improved tolerance to hypotonicity, an effect that can be reversed by the extracellular application of nucleotides (21,22).…”

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confidence: 99%

ICln159 Folds into a Pleckstrin Homology Domain-like Structure

Fürst

Schedlbauer

Gandini

et al. 2005

Journal of Biological Chemistry

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ICln is a multifunctional protein involved in regulatory mechanisms as different as membrane ion transport and RNA splicing. The protein is water-soluble, and during regulatory volume decrease after cell swelling, it is able to migrate from the cytosol to the cell membrane. Purified, water-soluble ICln is able to insert into lipid bilayers to form ion channels. Here ICln is a small (Ϸ25 kDa), multifunctional protein involved in regulatory mechanisms as different as cell volume regulation and RNA splicing (1, 2). Proteins involved in more than one regulatory mechanisms were recently defined as "connector hubs" (3) and play a pivotal role in cell function. Knock-out of such proteins is usually lethal. Accordingly, functional knockout of the ICln protein in mouse or nematode is lethal in the very early stages of development. No vital embryos can be obtained in either animal system (2, 4), which suggests a key role of ICln in cell homeostasis.ICln is water-soluble (1) and resides primarily in the cytosol (5), where it forms heteromultimeric complexes with (i) Sm proteins (6 -9), (ii) the arginine methyltransferase PRMT5 (6 -10), and (iii) cytoskeletal proteins such as ␤-actin, erythrocyte protein 4.1, or the non-muscle isoform of the alkali myosin light chain (5, 11-13). A fraction of ICln is associated with the cell membrane, and interaction with the membrane protein integrin ␣ IIb ␤ 3 has recently been demonstrated (14).During a hypotonic challenge, ICln migrates from the cytosol toward the cell membrane, suggesting a role for ICln in cell volume regulation (15). This regulatory mechanism is further substantiated by the finding that heterologous expression of ICln in Xenopus laevis oocytes is followed by the appearance of ion currents (1) resembling those elicited by swelling of mammalian cells (2, 16). Furthermore, ICln-specific antibodies (5) or antisense oligodeoxynucleotides (17, 18) leading to a specific knock-down of the ICln protein impair regulatory volume decrease (RVD) 1 in native cells. Conversely, overexpression of ICln in mammalian cells increases RVD currents during a hypotonic challenge (2,19,20). In bacteria, overexpression of ICln leads to an improved tolerance to hypotonicity, an effect that can be reversed by the extracellular application of nucleotides (21,22). The extracellular effect of nucleotides was also shown for heterologous expression of ICln in oocytes, and the putative binding site for nucleotides was identified (1, 23). The above mentioned findings point toward a channel function of ICln (1). The successful reconstitution of purified ICln in artificial lipid bilayers demonstrated that ICln can indeed form ion conducting channels, the selectivity of which depends on the lipid composition of the membrane (23-26).Another well documented function of ICln is its role in splicing. In the cytosol, ICln forms two separate complexes with splicing factors. One complex (6S) contains ICln and the Sm * The work was supported by the Austrian Science Foundation (Grants P13041-med, P15578, and P1711...

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“…A number of groups have demonstrated that integrins regulate potassium, calcium, or chloride fluxes either indirectly (17)(18)(19)(20)(21)(22) or directly (19, 21, 23, 26 -28). Vitronectin, but not fibrinonectin or laminin, selectively affects potassium currents in an Arg-Gly-Asp sequence-dependent manner in developing mouse hippocampal neurons (29).…”

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confidence: 99%

ICln, a Novel Integrin αIIbβ3-Associated Protein, Functionally Regulates Platelet Activation

Larkin

Murphy

Reilly

et al. 2004

Journal of Biological Chemistry

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A critical role for the conserved ␣-integrin cytoplasmic motif, KVGFFKR, is recognized in the regulation of activation of the platelet integrin ␣ IIb ␤ 3 . To understand the molecular mechanisms of this regulation, we sought to determine the nature of the protein interactions with this cytoplasmic motif. We used a tagged synthetic peptide, biotin-KVGFFKR, to probe a high density protein expression array (37,200 recombinant human proteins) for high affinity interactions. A number of potential integrin-binding proteins were identified. One such protein, a chloride channel regulatory protein, ICln, was characterized further because its affinity for the integrin peptide was highest as was its expression in platelets. We verified the presence of ICln in human platelets by PCR, Western blots, immunohistochemistry, and its co-association with ␣ IIb ␤ 3 by surface plasmon resonance. The affinity of this interaction was 82.2 ؎ 24.4 nM in a cell free assay. ICln co-immunoprecipitates with ␣ IIb ␤ 3 in platelet lysates demonstrating that this interaction is physiologically relevant. Furthermore, immobilized KVGFFKR peptides, but not control KAAAAAR peptides, specifically extract ICln from platelet lysates. Acyclovir (100 M to 5 mM), a pharmacological inhibitor of the ICln chloride channel, specifically inhibits integrin activation (PAC-1 expression) and platelet aggregation without affecting CD62 P expression confirming a specific role for ICln in integrin activation. In parallel, a cell-permeable peptide corresponding to the potential integrin-recognition domain on ICln (AKFEEE, 10 -100 M) also inhibits platelet function. Thus, we have identified, verified, and characterized a novel functional interaction between the platelet integrin and ICln, in the platelet membrane.

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Cell Swelling Stimulates Cytosol to Membrane Transposition of ICln

Cited by 54 publications

References 55 publications

Effect of complete protein 4.1R deficiency on ion transport properties of murine erythrocytes

Effect of complete protein 4.1R deficiency on ion transport properties of murine erythrocytes

ICln159 Folds into a Pleckstrin Homology Domain-like Structure

ICln, a Novel Integrin αIIbβ3-Associated Protein, Functionally Regulates Platelet Activation

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